Apparatuses for positioning within an internal channel

ABSTRACT

Methods and apparatuses for positioning medical devices onto (or close to) a desired portion of the interior wall of an internal channel, such as for scan imaging, for photodynamic therapy and/or for optical temperature measurement. In one embodiment, a catheter assembly has a distal portion that can be changed from a configuration suitable for traversing the internal channel to another configuration suitable for scan at least a spiral section of the interior wall of an internal channel, such as an artery. In one example, the distal portion spirals into gentle contact with (or close to) a spiral section of the artery wall for Optical Coherence Tomography (OCT) scanning. The spiral radius may be changed through the use of a guidewire, a tendon, a spiral balloon, a tube, or other ways.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 11/018,634, which was filed on Dec. 20, 2004 entitled “METHODSAND APPARATUSES FOR POSITIONING WITHIN AN INTERNAL CHANNEL”.

FIELD OF THE TECHNOLOGY

At least some embodiments of the present invention relate to scanimaging, treatment and/or measurement of the interior of an internalchannel, such as blood vessels.

BACKGROUND

Imaging technologies have been developed for the visualization of theinterior of an internal channel, such as a vein or artery. For example,current Optical Coherence Tomography (OCT) systems can image into tissueto a depth of about 1.2-1.7 mm. Analogous to ultrasound imaging, theimaging core of an OCT system projects an optical beam (e.g., a shortcoherence length infrared light) on the tissue and receives thereflected light from the tissue to construct an image of the tissue. AnOCT based imaging system can provide higher resolution imaging thancurrent ultrasonic systems, but to a shorter depth into the tissue.

FIG. 1 illustrates a prior art imaging assembly catheter. In FIG. 1, theimaging assembly includes a sheath (109) to house and guide the imagingcore, which includes an optical fiber (107), a GRIN lens (103) (gradedindex lens) and a prism (101). The sheath (109) has at least atransparent window (105), through which an imaging core may project anoptical beam on the tissue and receive the backscattered light. The GRINlens (103) focuses the beam coming from an optical fiber (107); and theprism (101) directs the beam perpendicular to the longitudinal axis ofthe imaging sheath (109). Backscattered/reflected light from the tissuesfollows the reverse path to return to the optical fiber (107). Opticalfibers have a core and a cladding. The light travels mostly in the core.The cladding has optical properties such that it bends any light thathappens to come out of the core back into the core, so no light islost/leaks out the side of the optical fiber. In practical systems forOCT, both the core and cladding are mostly glass with a few impuritiesadded to get the desired optical properties. The interference amplitudebetween an internal system reference beam and the reflected beam fromthe tissue is related to the intensity of the reflected light from thetissue at the reference beam path length. By scanning the reference beampath length, the amplitude of the reflected beam is scanned at differentdepths into the tissue to create an image along a line into the tissue.By also rotating (113) the imaging core, a two-dimensional image sliceof the tissue surrounding the prism (101) can be constructed. Bywithdrawing the imaging core inside the sheath (or both the sheath 109and the imaging core), image slices of the tissue may be recorded alonga length of the sheath 109 (or tissue) to provide three-dimensionaltissue imaging information. This withdrawal to gather tissue images iscommonly referred to as a pull back.

FIG. 2 illustrates the use of the prior art imaging assembly in scanningthe interior wall of an artery. The sheath (109) is inserted into anartery (121) with the imaging core, including the grin lens (103) andprism (101). The prism directs the optical beam to a point on the arteryto scan at different depths into the tissue at the point. Rotating theimaging core about the axial axis of the sheath (109) causes a scan inthe circumferential direction; and moving the imaging core along thesheath (109) causes a scan in the longitudinal direction. Thus, thecombined rotation and longitudinal movement of the imaging core allowsthe imaging core to scan the entire interior of the artery (121) for a360-degree of circumferential image of the artery.

In a prior art system illustrated in FIG. 2, the sheath (109) issubstantially straight in a straight section of the artery. Note that anartery is generally not straight; and the sheath generally follows theartery. For simplicity, the artery (or the vessel to be image) isconsidered straight and the sheath that follows the shape of the arteryis then also considered straight. When the sheath (109) is at about thecenter of the artery, the distance between the sheath (109) and theartery wall is D_(A) (123).

Current Optical Coherence Tomography (OCT) systems are not able to imagemore than about 1-2 mm into blood or tissue. Thus, the imaging depth ofthe OCT system is only about 1-2 mm. Theoretically, an OCT system may beable to image about 2-2.5 mm into tissue; but in practice, in thetissues of interest (vessel walls), a typical OCT system can image nodeeper than about 1.2-1.7 mm. Thus, the blood between the artery (121)and the sheath (109) can effectively cause blockage of the light signalfor the imaging of the artery wall and reduce the depth the OCT systemcan image into the artery wall.

Further, the wavelength of the light used in an OCT system may be shortenough for the light to interact with individual red blood cells. Use oflights of longer wavelengths may avoid the red blood cell interactionbut result in a loss of a desired image resolution. The red blood cellshave a slightly higher index of refraction than the plasma in which theyare suspended. In addition, the red blood cells are shaped like concavelenses so that the light may be redirected and refocused (diverged) byeach red cell it passes through on the way to the artery wall and backfrom the artery wall. In addition, there are light energy losses due toabsorption and path length changes due to scattering (reflection) by thered cells. Thus, the image quality decreases as the distance D_(A) (123)between the sheath and the artery increases. It is desirable to minimizethe effect of the blood's interference with the light from the imagingsystem as it propagates through the vessel towards the vessel wall andis reflected back to the device.

Currently, flushing is used to reduce the imaging signal (light)blockage effect of the blood. For example, saline can be injected intothe artery from the catheter to temporarily remove or dilute the bloodnear the region to be imaged. Various techniques and devices have beenused to flush blood from the imaging area with limited success. Forexample, flushing a coronary artery to remove blood from the field ofview is normally accomplished by injecting saline into the vessel to beimaged, either through a guide catheter or a catheter/sheath thatsurrounds/incorporates the imaging device. However there are severalproblems and limitations with flushing, especially in an artery.

First, when enough saline solution or other isotonic biocompatiblewater-based solution is introduced to replace or dilute the blood, theamount of oxygen in the solution is very small in comparison to theamount of oxygen contained in the blood. Thus, the time window forimaging is limited by the ischemic consequences of the solution on theheart muscle (e.g., reduction in blood flow). The longer the duration ofthe flush, the more severe the consequences are to the heart muscle.Since imaging is generally desired in patients usually already sufferingfrom ischemia or previous cardiac muscle ischemic tissue damage, thesafe/pain-free imaging time period is short.

Second, blood flow in coronary arteries is laminar and generally tendsto flow in streamlines, not mixing very rapidly with adjacentstreamlines. Thus, injected solutions tend to flow in their ownstreamlines, leaving some areas of blood flow not completelydisplaced/mixed or leaving eddies of blood at branch points or at areasprotected/created by the presence of the imaging device.

Third, most water-based flushing solutions have a viscosity that issignificantly less than that of blood. Thus, the flow rate of the flushmust exceed the normal flow rate of the blood in the vessel in order tocreate enough pressure in the vessel to exceed the blood pressure anddisplace the blood. In other words, the resistance to flow in the vesselis lower for the flush than for the blood.

As the flush replaces the flowing blood, an ever-increasing flow rate ofthe flush is required. For example, the decreased resistance of theflush requires more overall fluid (e.g., flush) to maintain the naturalflow rate. Moreover, the vessel will dilate in response to the ischemicproperties caused by an increased amount of oxygen deficient fluid inthe vessel. Thus, the flush flow rate must be increased until a peakflow rate is reached, wherein the flush effectively completely replacesthe blood in the artery. The volume of flush required to achieve thispeak flow rate can be quite high during extended imaging periods, likethose commonly used with IVUS (Intravascular Ultrasound).

Fourth, in most injection configurations, the required high flush flowrate enters the artery via a relatively small flow cross section,resulting in a very high injection velocity. This may create highvelocity jets of flush, which can damage vessel walls. Additionally, thepressures and volumes required are not easily accomplished by manualinjection. Therefore, an automated injection device is desirable.

Alternatively, injection of a fluid more viscous than saline (e.g., acontrast agent) may utilize a lower flow rate, but the catheterinjection pressure is relatively unchanged due to the higher viscosity.A high viscosity flush also increases the time required to wash out theflush (e.g., longer ischemia time). Moreover, contrast agents are quiteexpensive relative to normal flushing solutions.

Several methods to deal with these problems of a typical flush have beenproposed in the past. For example, oxygenated blood can be withdrawnfrom the patient, and certain materials may be added to the blood toincrease the index of refraction of its plasma to match that of the redblood cells. This oxygenated blood, with a higher index of refraction ofits plasma, can then be used as the flush. Alternatively, the materialsto increase the index of refraction of the plasma may be addedsystemically without withdrawing any blood from the patient.

In either case, such a procedure would eliminate/effectively minimizethe lens effect and the reflection effect of the red blood cells. Sincethe red blood cells are oxygenated, ischemia is not a problem. It hasbeen reported that contrast can be used to make this index of refractionchange to the plasma.

Changing the index of refraction on a systemic level is very difficultand can be toxic. It is easier and faster to perform the index ofrefraction change with blood withdrawn from the body. However, changingthe index of refraction outside of the patient's body requires extraequipment and a time-consuming index matching procedure and introducesissues involving increased blood exposure (e.g., to the environment).Moreover, the streamline and injection problems discussed above wouldstill be a challenge, and hemolysis (e.g., the destruction ordissolution of red blood cells, with subsequent release of hemoglobin)could be an added issue to consider.

Photodynamic therapy may be administered within a vessel to treatvarious conditions. For example, light (e.g., blue light and/orultraviolet light) may be used to destroy (e.g., cell lysis) or treatvarious target tissues such as tumors and atheromas, including thincapped fibroathroma (“TCFA”) or vulnerable plaque. A similar blockage ofthe light used in photodynamic therapies may also be a problem and mayrequire similar saline flushing or blood dilution.

SUMMARY OF THE DESCRIPTION

Methods and apparatuses for scanning a desired portion of the interiorwall of an internal channel, such as for scan imaging a blood vessel,for photodynamic therapy and for optical temperature determination, aredescribed here. Some embodiments are summarized in this section.

In one embodiment, a catheter assembly has a distal portion that can bechanged from a configuration with a small overall radius suitable fortraversing the internal channel to another configuration that issuitable for scanning at least a section of the interior wall of aninternal channel, such as an artery. In one example, to eliminate orreduce the blockage effect of the blood in Optical Coherence Tomography(OCT) scanning, the distal portion spirals into gentle contact with (orcloser to) a section of the artery wall for imaging along a spiral pathfor the detection of a significant vulnerable plaque. The spiral radiusmay be changed through the use of a guidewire, a tendon, a spiralballoon, a tube, or others. In another example, a spiral balloon is usedto clear the blood out of the way between a spiral section of the vesselwall and the imaging sheath without blocking the blood flow in theartery. In one example, a catheter assembly similar that for scanimaging is used for the effective application of light to vessel walltissues for purposes of photodynamic therapy. To reduce the blockageeffect, the core for the application of light is housed in the sheaththat can spiral into gentle contact with (or closer to) a section of theblood vessel wall, or in the sheath that has a balloon inflatable toclear the blood between the sheath and the section of the blood vesselwall, to ensure that the desired section of the vessel wall wasirradiated with the light to an effective/sufficient/desired degree. Inone example, a similar catheter assembly is used for the effective lightcollecting without projecting light, such as for optical temperaturedetermination. To reduce the blockage effect, the core for the lightreceiving device (e.g., such as a fiber optic assembly, a core or animaging core for connection to optical temperature determinationdevices) is housed in the sheath that can spiral into gentle contactwith (or closer to) a section of the blood vessel wall, or in the sheaththat has an outside balloon inflatable to clear the blood between thesheath and the section of the blood vessel wall.

In one aspect of an embodiment, an elongated assembly includes: aproximal portion; and, a distal portion, the distal portion to beinserted into a vessel, the distal portion controllable throughoperating at the proximal portion. The distal portion includes: anelongated sheath to house a core movable within the sheath to scan aportion of the vessel; and, a guide structure coupled with the sheath.The core is capable of at least one of: projecting an optical beam ontoa portion of the vessel and receiving a light from a portion of thevessel. The guide structure is controllable through the proximal portionto reduce an overall diameter of the distal portion into a firstconfiguration; and the guide structure is controllable through theproximal portion to increase the overall diameter of the distal portioninto a second configuration. In one embodiment, the sheath is in aspiral shape in the second configuration. The distal portion is totraverse the vessel in the first configuration; the core is to movealong the sheath to scan for an image of the vessel in the secondconfiguration with reduced signal blockage; and signal blockage due toblood in the vessel between outside of the spiral shape of the sheathand the vessel in the second configuration is smaller than in the firstconfiguration without the need for flushing.

In one embodiment, the distal portion of the elongated assembly does notseverely block a flow of the blood or other tissue in the vessel in thesecond configuration (e.g., in second configuration the distal portiondoes not block a flow of the blood in the vessel significantly more thanin the first configuration).

In one embodiment, the assembly further includes the core housed withinthe sheath; the core projects an optical beam (e.g., a short coherencelength light) and to receive a reflected light for optical coherencetomography.

In one example of an embodiment, a pitch length of the spiral shape isless than five times an imaging depth of the core; in one example of anembodiment, a pitch length of the spiral shape is less than a size of asignificant vulnerable plaque on a blood vessel plus two times animaging depth of the core (e.g., the depth into blood and tissue thatcan be imaged). In one embodiment a pitch length of the spiral is lessthan ten times the radius of the vessel.

In one example of an embodiment, a diameter of the spiral shape issubstantially equal to a diameter of the vessel in the secondconfiguration. Thus, the spiral gently contacts the vessel wall or isclose to the vessel.

In one example of an embodiment, the distal portion of the elongatedassembly has a stiffness and is formed to be a spiral shape in absenceof external constrains; a straight guidewire is insertable into thedistal portion of the elongated assembly to straighten the distalportion of the elongated assembly into the first configuration.

For example, the guide structure has a guidewire lumen; and the assemblyfurther includes: a guidewire, a segment of which is operable throughthe proximal portion of the elongated assembly to slide within theguidewire lumen. The segment of the guidewire has a stiffness and isformed to be substantially straight in absence of external constraints.The distal portion of the elongated assembly has a stiffness and isformed to be a spiral shape in absence of external constrains. Thedistal portion of the elongated assembly is in the first configurationwhen the segment of the guidewire is in the guidewire lumen tostraighten the distal portion of the elongated assembly. The distalportion of the elongated assembly is in the second configuration whenthe segment of the guidewire is out of the guidewire lumen. In oneexample, the sheath is substantially straight when in the firstconfiguration; and a radius of the spiral shape of the sheath issubstantially equal to a radius of the vessel when in the secondconfiguration and in the vessel.

In one example of an embodiment, the distal portion of the elongatedassembly has a stiffness and is formed to be substantially straight inabsence of external constrains; a spiral guidewire is insertable intothe distal portion of the elongated assembly to spiral the distalportion of the elongated assembly into the second configuration.

For example, the guide structure has a guidewire lumen; and the assemblyfurther includes: a guidewire, a segment of which operable through theproximal portion of the elongated assembly to slide within the guidewirelumen. The segment of the guidewire has a stiffness and is formed to bein a spiral shape in absence of external constraints. The distal portionof the elongated assembly has a stiffness and is formed to besubstantially straight in absence of external constrains. The distalportion of the elongated assembly is in the first configuration when thesegment of the guidewire is out of the guidewire lumen. The distalportion of the elongated assembly is in the second configuration whenthe segment of the guidewire is in the guidewire lumen to spiral thedistal portion of the elongated assembly. In one example, the sheath issubstantially straight when in the first configuration; and a radius ofthe spiral shape is substantially equal to a radius of the vessel whenin the second configuration and in the vessel. In one example, theassembly has a middle portion connected to the distal portion of theelongated assembly; the middle portion of the elongated assembly has astiffness and is formed to be substantially straight in absence ofexternal constraints; and the middle portion of the elongated assemblyremains substantially straight when the segment of the guidewire is inthe middle portion of the elongated assembly. In one example, anotherstraight guidewire is inserted into the guidewire lumen to position orreposition the distal portion of the elongated assembly at differentlocations.

In one embodiment, the guide structure is operable at the proximalportion of the elongated assembly to: reduce a spiral length of thesheath to increase a spiral diameter of the sheath; and increase thespiral length of the sheath to reduce the spiral diameter of the sheath.In one embodiment, the guide structure is operable at the proximalportion of the elongated assembly to: reduce a number of spiral turns ofthe sheath to increase a spiral diameter of the sheath; and increase anumber of spiral turns of the sheath to reduce the spiral diameter ofthe sheath.

For example, the guide structure includes: a tube; and a substantiallystraight guide member. A portion of the guide member is slidable intothe tube. The guide member has a distal end extending outside the tube.The sheath has a distal end coupled to the distal end of the guidemember. The sheath has a proximal end coupled to the tube. The sheathspirals around the guide member. The sheath wraps against the guidemember in the first configuration when the portion of the guide memberis out of the tube. The sheath spirals against the vessel in the secondconfiguration when a portion of the guide member is withdrawn into thetube. In one example, the guide member is rotatable with respect to thetube; when the guide member rotates with respect to the tube in a firstdirection, a diameter of the spiral shape of the sheath is increased;when the guide member rotates with respect to the tube in a seconddirection, the diameter of the spiral shape of the sheath is decreased.

In one embodiment, the guide structure includes: a guide member; and, atendon coupled to the guide member. The tendon bends the guide memberinto a spiral in the second configuration when the tendon is in tension;and the guide member has a stiffness and is formed to be substantiallystraight in the first configuration when the tendon is not in tension.In one example, the guide member has a tendon lumen spiraling around theguide member to house the tendon; and the sheath spirals around theguide member on an opposite side of the tendon lumen. In one example,the elongated assembly has a middle portion connected to the distalportion of the elongated assembly; the middle portion of the elongatedassembly includes a plurality of tendons; the plurality of tendons inthe middle portion of the elongated assembly connected to the tendon inthe distal portion of the elongated assembly to provide a tension forceto bend the guide member; and the tension force is distributed in theplurality of tendons in the middle portion of the elongated assembly toreduce bending moment to the middle portion of the elongated assemblydue to the tension force.

In one embodiment, the guide structure includes: a guide member, whichis substantially straight; and a balloon outside the guide member. Thesheath spirals over the balloon; a spiral diameter of the sheathincreases in the second configuration when the balloon is inflated; andthe spiral diameter of the sheath decreases in the first configurationwhen the balloon is deflated. In one example, the balloon is of a spiralshape, spiraling around the guide member.

In one embodiment, the guide structure includes: a substantiallystraight guide member, the sheath spiraling around the guide member;and, a balloon containing the sheath. The distal portion of theelongated assembly is in the first configuration when the balloon isdeflated; and the distal portion of the elongated assembly is in thesecond configuration when the balloon is inflated. In one example, theballoon spirals around the guide member.

In one aspect of an embodiment, the sheath has a spiral shape in avessel; the sheath houses a core movable along the sheath to scan atleast a spiral portion of the vessel. The core capable of at least oneof: projecting an optical beam onto a portion of the vessel andreceiving a light from a portion of the vessel. In one example of anembodiment, the sheath has a guidewire lumen; and a diameter of thespiral shape is substantially equal to the diameter of the vessel. Inone example of an embodiment, the sheath is capable of being straightenin the vessel when a guidewire is inserted into the guidewire lumen. Inone example of an embodiment, the sheath is capable of being shaped intothe spiral shape in the vessel when a spiral guidewire is inserted intothe guidewire lumen. In one example of an embodiment, the sheath spiralsaround a guide member with a distal end coupled to the guide member; thesheath has a proximal end movable along the guide member toward thedistal end to increase a spiral diameter of the sheath and away from thedistal end to decrease the spiral diameter of the sheath; separately orin addition, the proximal end of the sheath is rotatable around theguide member in a first direction to increase a spiral diameter of thesheath and in a second direction to decrease the spiral diameter of thesheath. In another example, the sheath spirals around a guide memberwith one end coupled to a distal end of the guide member and another endmovable relative to a proximal end of the guide member; the proximal endof the guide member is rotatable relative to the sheath in a firstdirection to increase a spiral diameter of the sheath and in a seconddirection to decrease the spiral diameter of the sheath; separately orin addition, the guide member is movable longitudinally in one directionto reduce a spiral diameter of the sheath and in the opposite directionto increase the spiral diameter of the sheath. In one example, theproximal end is attached to the tube. In one example, the guide memberhas a tendon lumen spiraling around the guide member; a tendon housedinside the tendon lumen has a distal end attached to the guide member;the tendon bends the guide member into a spiral shape when the tendon isin tension; and the guide member is substantially straight when thetendon is not in tension. In one embodiment, a balloon is within thespiral shape of the sheath; the balloon is inflatable to increase aradius of the spiral shape of the sheath; and the balloon is deflatableto decrease the radius of the spiral shape of the sheath. In oneembodiment, the balloon is outside a substantially straight guidemember. In one example, the balloon is of a spiral shape, wrappingaround the guide member. In one example, the sheath spiraling around asubstantially straight guide member; a spiral balloon is mounted toenclose the sheath.

In one aspect of an embodiment, an assembly to be inserted into avessel, includes: a sheath to house a core movable along the sheath toscan at least a portion of a vessel; and a balloon enclosing at least aportion of the sheath along the sheath. The core is capable of at leastone of: projecting an optical beam onto a portion of the vessel andreceiving a light from a portion of the vessel. When inflated theballoon clears at least a portion of a light path between the sheath andthe vessel to reduce blockage. In one example, the balloon is of aspiral shape, spiraling around the sheath. The sheath has a stiffnessand is formed to remain substantially straight when the balloon of thespiral shape is inflated. In one example, the core projects an opticalbeam to receive a reflected light for optical coherence tomography; andthe balloon is substantially transparent to the optical beam. In oneexample, the balloon is movable relative to the sheath (e.g., slidablealong the sheath or rotatable about the sheath).

In one aspect of an embodiment, an assembly to be inserted into a vesselincludes a plurality of spiral sheaths twisted together to host one ormore cores capable of at least one of: projecting an optical beam onto aportion of the vessel and receiving a light from a portion of thevessel. In one example, each of the spiral sheaths has a distal endcoupled to the distal end of a guide member; and each of the spiralsheaths has a proximal end coupled to a tube. The tube is movable withrespect to the guide member to change the spiral radius of the sheaths.In one example, a core is insertable from the tube into each of theplurality of spiral sheaths; in another example, each of the pluralityof spiral sheaths houses an individual core.

The present invention includes apparatuses and methods, which operatethese apparatuses. The methods and apparatuses can be used for scanimaging, for optical temperature determination, for photodynamictherapy, and for other applications that can benefit from reducinginterference from the blood in the blood vessel. The core housed in thesheath can be used to project light, to receive light, or to projectlight and receive reflected light (or high frequency ultrasound).

Other features of the present invention will be apparent from theaccompanying drawings and from the detailed description, which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 illustrates a prior art imaging assembly for use with a catheter.

FIG. 2 illustrates the use of the prior art imaging assembly in scanningthe interior wall of an artery.

FIG. 3 illustrates an imaging sheath according to one embodiment of thepresent invention.

FIGS. 4-5 show geometric relations of a spiral, which may be used indesigning an imaging sheath according to one embodiment of the presentinvention.

FIGS. 6-8 illustrate an imaging assembly with a pre-formed spiralimaging sheath according to one embodiment of the present invention

FIGS. 9-14 illustrate imaging assemblies with a pre-formed spiralguidewire according to embodiments of the present invention.

FIGS. 15-17 illustrate an imaging assembly with a tube according to oneembodiment of the present invention.

FIGS. 18-22 illustrate an imaging assembly with a tendon according toone embodiment of the present invention.

FIGS. 23-26 illustrate an imaging assembly with a spiral balloonaccording to one embodiment of the present invention.

FIGS. 27-30 illustrate an imaging assembly with a regular balloonaccording to one embodiment of the present invention.

FIGS. 31-38 illustrate an imaging assembly with a plurality of imagingsheaths according to one embodiment of the present invention.

FIGS. 39-42 illustrate an imaging assembly with a spiral ballooncovering the imaging sheath according to one embodiment of the presentinvention.

FIGS. 43-46 illustrate an imaging assembly with a straight imagingsheath enclosed in a spiral balloon according to one embodiment of thepresent invention.

FIGS. 47-50 illustrate an imaging assembly with a plurality of tendonson a portion of the assembly to reduce bending according to oneembodiment of the present invention.

FIGS. 51-52 illustrate an assembly to balance the forces in two tendonsfor an imaging assembly according to one embodiment of the presentinvention.

FIG. 53 illustrates a catheter assembly according to one embodiment ofthe present invention.

FIG. 54 illustrates a method of using an imaging assembly according toone embodiment of the present invention.

DETAILED DESCRIPTION

The following description and drawings are illustrative of the inventionand are not to be construed as limiting the invention. Numerous specificdetails are described to provide a thorough understanding of the presentinvention. However, in certain instances, well known or conventionaldetails are not described in order to avoid obscuring the description ofthe present invention. References to one or an embodiment in the presentdisclosure are not necessarily references to the same embodiment; and,such references mean at least one.

At least one embodiment of the present invention seeks to eliminate orreduce the effect of blood on the imaging of a blood vessel without theneed for flushing. While flushing the blood vessel can reduce the effectof the blood on the image quality, flushing has a few drawbacks andproblems. In at least one embodiment of the present invention, animaging sheath spirals against the blood vessel for imaging so that theimaging sheath and a desired section of the vessel wall are very closeto each other, eliminating the need for flushing.

A vulnerable plaque that can rupture and cause a damaging cardiacischemic event is highly likely large enough to occupy a significant arcsection of the vessel and/or a significant length of the coronary. Thus,a full 360-degree of circumference image of the vessel is not necessaryfor the detection of a significant vulnerable plaque. Thus, imaging thevessel longitudinally at intervals greater than that of current OCT(Optical Coherence Tomography) or IVUS (intravascular high frequencyultrasound) systems would detect a significant vulnerable plaque.

To detect a significant vulnerable plaque it would only be necessary toimage at the vessel wall in a spiral pattern down the length of thevessel with the orthogonal distance between adjacent spiral loops beingshorter than the minimum length of the vulnerable plaque deemed to besignificant plus 2 times the effective imaging depth. For example, ifthe sheath of the imaging core is positioned against the vessel wall ina spiral pattern at about a 4 mm apart in the direction orthogonal tothe sheath, all of the vessel wall can be imaged when the effectiveimaging depth is 2 mm. If the distance is 6 mm, under the sameassumptions, any vulnerable plaque about 2 mm or more in length down thevessel can be imaged and thus detected. Because the imaging sheath is incontact with (or very near) the vessel wall, flushing is not necessary.

Embodiments of the present invention provide many ways to create apercutaneous system that places the imaging sheath of an OCT systemgently (to avoid wall damage or rupturing of a vulnerable plaque)against or close to the vessel wall in a manner that will notsignificantly reduce vessel blood flow and will thus allow imaging forperiods much longer than systems that require flushing. The imaging coreof an OCT system may be about 0.004-0.005 inch in diameter. An imagingsheath with a 0.001 inch wall and 0.001 inch clearance will have adiameter of 0.008 inch. Arteries that are currently accessed, imaged andtreated with procedures like angioplasty are generally about 0.08″(about 2 mm) or more in Inside Diameter (ID). Thus, there is plenty ofroom for other components in the imaging assembly and for blood flow.

For example, one way is to form the imaging sheath with a guidewirelumen into a spiral at its distal imaging section. With the guidewire inplace and the imaging core distal, the sheath is straightened by thestiffness of the guidewire and guided into a position for imaging overthe guidewire. The guidewire engagement to the catheter is preferablyeither an RX (Rapid eXchange) or OTW (Over The Wire) style. In an RXcatheter, the guidewire only engages a distal portion of the catheter,where “engage” refers to that guidewire is contained within a lumen ofthe catheter. In an OTW catheter, the guidewire engages the full lengthof the catheter. The guidewire can thus be shorter with an RX catheter.The length of the RX guidewire engagement of the catheter is chosen suchthat the portion of the catheter that is exposed to the vessel alwaysengages the guidewire, so the vessel is not exposed to both the bareguidewire and the catheter at the same location. In an RX catheter, thelength along the catheter where the guidewire doesn't engage thecatheter (the catheter and the bare guidewire are separate and runparallel to each other) is contained within the guide catheter and exitsthe proximal end of the guide (and RHV). If the guidewire engagement isso short on the distal end of the catheter that both the catheter andthe bare guidewire are exposed to the vessel, the engagement style iscalled a “tip monorail”. After the withdrawn of the stiff section of theguidewire proximal to the imaging section, the sheath spirals intocontact with or closer to the vessel wall. After the imaging pullback(pulling back the imaging core along the spiral sheath to scan for animage), the operator can advance the guidewire back to its formerposition to straighten the sheath. The imaging core can also be advancedback to its former position. Then, the sheath can be repositioned to thenext imaging position in the vessel.

In a similar embodiment, the guidewire lumen may be eliminated, at leastfrom the distal section of the catheter, if the catheter or imagingsheath is designed such that the imaging core and guidewire may replaceeach other within the imaging sheath. That is, with the imaging corewithdrawn from the distal section, the guidewire occupies the lumen ofthe imaging sheath, causing the imagining sheath to straighten duringcatheter advancement and positioning. Once in position, the guidewire iswithdrawn from the imaging sheath, allowing the imaging sheath tospiral, and then the imaging core is advanced into the imaging sheath.In this embodiment the catheter is either a single lumen device over itsfull length or the catheter is a single lumen device in its distalsection and that lumen splits into two lumens in its proximal section.

Alternatively, the spiral is not formed into the sheath. After thestraight guidewire is withdrawn, a spiral shaped guidewire (or wire orelongated material) is inserted into the guidewire lumen to cause thesheath to spiral against or closer to the vessel wall for imaging.

Another way is to form an imaging sheath section without a guidewirelumen into a spiral. The distal end of the imaging sheath is attachednear the distal end of a guidewire (or a tube or a guide member thatwill accommodate the guidewire). The proximal end of the imaging sheathis attached to a tube, one lumen of which provides a continuous lumen toaccommodate the imaging core and the other slidably (longitudinallyand/or rotationally) engages the guidewire (or the tube or the guidemember that will accommodate the guidewire). When the tube is heldstill, the guidewire can be advanced to collapse the spiral andwithdrawn to expand the spiral (through changing the spiral pitch); andthe guidewire can be rotated in one direction to reduce the spiraldiameter and on the opposite direction to increase the spiral (throughchanging the number of spiral turns). Alternatively, the guidewire maybe held still with respect to the body. In this case, when the tube ismoved proximally (and/or rotated in the proper direction), the spiralcollapses and spirals around the distal end of the guidewire (or thetube or the guide member that will accommodate the guidewire). In thisposition, the guidewire/catheter system can be delivered into the vesseland used to image small vessels. When the tube is moved distally (and/orrotated in the opposite direction), the spiral expands and comes incontact with or closer to the vessel wall for imaging. If the spiraldoes not expand enough (or expands too much) for the desired imaging dueto tube distal motion, rotating the guidewire (or the tube or a guidemember that will accommodate the guidewire) relative to the tube in theproper direction can adjust the size of the spiral. Thus, in general,the relative movement between the guidewire and the tube, rotationallyand/or longitudinally, can be controlled to expand or collapse thespiral. In a practical system, it is typically easier to move(rotationally and/or longitudinally) the guidewire than the tube at theproximal end. Moving the tube and the proximal end of the imaging sheathcan be more difficult to accomplish, as the tube has a large OutsideDiameter (OD) which is subjected to pressure from outside that causesfriction and difficulty in moving the tube. On the other hand, theguidewire (or guide member) is mostly inside the tube and has a small ODwhich limits the frictional forces required to move the guidewire (orguide member). The clearances and materials can be easily chosen so thatthe guide member or guidewire rotates and/or translates freely insidethe tube. The proximal end of the catheter system may contain a handlewith indications or marks that guide the operator in this adjustment toprevent (limit) the applied forces and displacements from damaging thecatheter system and/or the vessel wall. Such a system allows a greaterrange of adjustment to fit the vessel and does not require amanipulation of the guidewire during the imaging procedure. The designof such a system does not require the very precise control of theflexural properties of the imaging sheath and guidewire compared to thepreviously described systems without a tube or guide member.

A further way is to form the imaging sheath with an imaging core lumen,a guidewire lumen and a tendon lumen(s). The catheter is constructed asan imaging deflection catheter. The tendon lumen spirals around thecatheter in the distal imaging section of the catheter. The imaging corelumen spirals around the opposite side of the tendon lumen. Theguidewire lumen is in the middle, between the tendon lumen and theimaging core lumen. When the catheter is in place, pulling on the tendonof the deflection catheter causes the imaging section to form into aspiral and come into contact with or move closer to the vessel wall forimaging. The guidewire may be withdrawn from the imaging section priorto pulling on the tendon, if desired. As before, the guidewire lumen canbe eliminated, at least from the distal section of the catheter, whenthe catheter or imaging sheath is designed such that the imaging coreand guidewire can replace each other within the imaging sheath.

A further way is to place a spiral balloon on a catheter and put animaging sheath on the outside of the balloon. The spiral balloon allowsblood flow and positions the imaging sheath (and the imaging core) on ornear the vessel wall when inflated. Alternatively, the imaging sheathmay spiral on the outside of a regular balloon on a reperfusion catheterchassis. Although the regular balloon causes more blockage of the bloodflow in the vessel, the reperfusion lumen of the catheter chassisprovides a channel for blood flow in the vessel. In systems with theimaging sheath positioned on the outside of balloon, it is preferredthat the imaging sheath be attached at or near the distal end of theballoon's major Outside Diameter (OD) and the imaging sheath be designedto accommodate the length changes caused by the balloon's inflation.This can be done in various manners, but the simplest is to form theimaging sheath into one or more telescoping sections and to eitherloosely constrain the imaging sheath to the balloon with loops or achannel(s) or to attach the imaging sheath to the balloon OD betweentelescoping sections.

Alternatively, the imaging sheath is within a transparent/translucentspiral balloon. The shape and length of the imaging sheath does notchange as the balloon is inflated or deflated. When the balloon isinflated, the spiral balloon pushes the blood out put the way betweenthe imaging sheath and a spiral section of the vessel wall but stillallows blood flow in the vessel. The balloon may be deflated,repositioned (rotated and/or moved longitudinally relative to thevessel) and re-inflated for imaging different spiral sections of thevessel wall.

The imaging sheath (a lumen wall, an imaging assembly wall, a guidemember or a portion of the imaging core) can contain a radiopaquemarker(s), radiopaque filler material and/or OCT detectable featuresthat can be used to identify where in the spiral a vulnerable plaque isimaged. Thus, in conjunction with fluoroscopy, an imaged feature of thevessel wall may be located relative the vessel anatomy for treatmentand/or further examination. Fluoroscopy may also aid in re-positioningthe imaging assembly/catheter to obtain a better image of a vesselfeature. If the treatment is to be a photodynamic treatment where thelight is sent to the treatment site via the imaging core, OCT detectablefeatures of the vessel and/or the imaging sheath can provide sufficientlocation information to guide the treatment.

Further details for various embodiments of the present invention aredescribed below. From this description, a person skilled in the art canenvision many variations in the scanning procedures, the designs of thesheath, designs of the imaging assembly and the designs of the formed ormanipulated spiral based on the examples provide below.

FIG. 3 illustrates an imaging sheath according to one embodiment of thepresent invention. In FIG. 3, the imaging sheath (201) spirals withinthe artery (203) so that the imaging sheath (201) spirals very close toor in contact with the artery wall. Since the spiral radius of theimaging sheath (201) is substantially equal to the radius of the artery(203), the distance D_(v) (205) between the outside of the spiral of theimaging sheath and the artery wall is significantly reduced. Thus, atleast a spiral path around the artery wall can be scanned from theimaging sheath at close range without a significant blockage effect fromthe blood. In FIG. 3, for illustration purpose, the artery is shown asstraight. It is understood that an artery or vessel is generally notstraight. However, it is understood that in this description, theportion of the vessel to be imaged is substantially straight whencompared to the spiral of the imaging sheath.

In one embodiment of the present invention, the spiral of the imagingsheath gently touches the artery or vessel wall so that the distanceD_(v) is zero or almost zero along a portion of the length of theimaging sheath. Indeed, the spiral of the imaging sheath may gentlydeform the wall of the vessel, such that the vessel wall may conform tocover a portion of the OD of the imaging sheath.

In one embodiment of the present invention, the shape of the imagingsheath is controllable to have one configuration as illustrated as inFIG. 3 for the imaging of the artery and another configuration which hasa substantially smaller overall radius so that the imaging sheath can bemore easily and atraumatically moved within the artery/vessel or moreeasily delivered to the artery/vessel by conventional devices such asguide catheters and guidewires.

Examples of using an imaging core that projects and receives a beam of ashort coherence length infrared light for OCT scanning (e.g., through aGRIN lens and a prism) are illustrated and/or discussed in manyembodiments. Any light-based image scanning or photodynamic therapysystem can also be used with these embodiments. It is understood thatany light-based imaging scanning system known in the art can be used.Further, it is understood that other forms of light delivering devices,such as photodynamic therapy light delivery devices, or other forms oflight collecting devices, such as optical temperature determinationdevices, can be used with the embodiments of the present invention.Furthermore, other types of imaging scanning systems (e.g., highfrequency ultrasound based systems) may also be used with the presentinvention. Thus, the term “imaging core” includes light deliveringdevices (e.g., as in photodynamic therapy), light receiving devices(e.g., as for optical temperature determination), light(electro-magnetic waves, visible or not) delivering and receivingdevices (e.g., as in an OCT system), and delivering and/or receivingdevices for energy that propagates in waves (e.g., high frequencyultrasound) and thus suffer from problems due to interactions withblood.

Additionally, many of the embodiments of the present invention can alsobe used with other devices where proximity to the vessel wall isdesired. For instance, a temperature sensor (i.e. a thermocouple, athermistor) may be used to measure vessel wall temperature changes tohelp identify a vulnerable plaque. In another instance the imagingsheath may be made of a material that is permeable to a chemical that itis desired to detect in the vessel wall and the core contains at least aportion of a detector system for that chemical.

FIGS. 4-5 show geometric relations of a spiral, which may be used indesigning an imaging sheath according to one embodiment of the presentinvention. The spiral (217) wraps around a cylindrical surface (215).The cylindrical surface (215) has a diameter D (213), which is equal tothe spiral diameter of the spiral (217). The spiral length of one turnof the spiral (e.g., from point P₁ (221) to point P₂ (223)) is the pitchlength L_(p) (211) of the spiral (217).

A cylindrical surface (e.g., 215) can be unwrapped as a flattenedsurface without stretching. If the cylindrical surface (215) is cutalong the straight line P₁P₃ (221 to 225) and unwrapped (230) as aflattened surface 240. The portion of the spiral 217 between points P₁(221) and P₂ (223) becomes a straight line (247) between points P′₁(241) and P′₂ (243) on the flattened surface 240.

Thus, the wind angle θ can be determined from the pitch length L_(p) ofthe spiral and the circumference πD. The length of the straightenedimaging sheath for each turn of the spiral is L₁=[(πD)²+L_(p) ²]^(1/2).

In FIG. 4, one can see the following geometric relations.

sin θ=L _(p) /L ₁

cos θ=πD/L ₁

tan θ=L _(p) /πD

Since (πD)²=L₁ ²−L_(p) ², one can see that for a given length of imagingsheath (e.g., L₁), the spiral radius (D/2) increases when the spirallength (L_(p)) is reduced; similarly, the spiral diameter (D) decreaseswhen the spiral length (L_(p)) is increased.

The relation between the total length (L_(T)) of the straightenedimaging sheath and the length of the straightened imaging sheath foreach turn of spiral is:

L ₁ =L _(T) /N _(T)

where N_(T) is the total number of spiral turns.

Thus, reducing the number of spiral turns increases the length of theimaging sheath for each spiral turn, which increases the spiral diameterif the pitch length L_(p) is kept constant. Similarly, increasing thenumber of spiral turns decreases the length of the imaging sheath foreach spiral turn, which decreases the spiral diameter if the pitchlength L_(p) is kept constant.

The distance between the adjacent turns of the spiral on the flattenedsurface 240 is

L _(pp) =L _(p) cos θ=πDL _(p) /L ₁

Since the imaging system scans perpendicular to the longitudinaldirection, a strip (249) on the flattened surface (240) is scanned andimaged. If the half width of the strip (249) is I_(D) (239), the gapwidth that is not scanned is

W _(n) =L _(pp)−2 I _(D) =πDL _(p) /L ₁−2 I _(D)

Let the diameter of a significant vulnerable plaque be S_(p). Thus, thescanning along the spiral will not miss the vulnerable plaque, if

W_(n)<S_(p).

The half width I_(D) (239) of the imaged strip (249) is measured on theflattened surface (240). FIG. 5 shows the geometric relation between thehalf width I_(D) (239) of the imaged strip and the imaging depth I_(o)(261). The projection of I_(D) (239) along the longitudinal direction isI_(D) cos θ (263); and the projection of I_(D) (239) along thecircumference is I_(D) sin θ (263). Since the angle β (253) is

β=(I _(D) sin θ)/R

where R=D/2 is the radius of the spiral, the lengths of line segmentsP_(x3)P_(x1) (267) and P_(x3)P_(x2) (269) are (R−R cos β) and (R sin β)respectively. Thus, the relation between the imaging depth I_(o) and thehalf width I_(D) is:

I _(o) ²=(I _(D) cos θ)²+(R−R cos β)²+(R sin β)²

Thus, when the imaging depth L is known, the above equation can be usedto determine the half width of the imaged strip. When the angle β issmall, I_(D) is approximately equal to I_(o).

When the spiral surface is not on the surface of the blood vessel, whichhas a radius of R_(v), the relation between the imaging depth I_(o) andthe half width of the imaged strip is:

I _(o) ²=(I _(D) cos θ)²+(R−R _(v) cos β)²+(R sin β)²

where

β=(I _(D) sin θ)/R _(v)

Although the above spiral geometry illustrates a perfect spiral, it isunderstood that in this description the term “spiral” is also for shapesthat approximate a perfect spiral, which may have a pitch length varyingfrom point to point and a spiral radius varying from point to point.Thus, the spiral radius and spiral pitch length for a general spiraldiscussed in this description are average measurements of a local regionof the spiral. This geometric description provides the basis fordetermining the desired or resulting imaging conditions of spiralimaging sheath designs in vessels.

In one embodiment of the present invention, the spiral of the imagingsheath is to gently contact the interior of the blood vessel so that Ris approximately equal to R. In one embodiment, the pitch length of thespiral is smaller than the size of a significant vulnerable plaque in ablood vessel wall plus two times an imaging depth of the imaging coresuch that at least a portion of the significant vulnerable plaque willbe in the imaged strip. Alternatively, the pitch length may be longer,such that a significant vulnerable plaque may not be imaged. To ensurethat a significant vulnerable plaque is detected the spiral of theimaging sheath is moved into different positions (e.g., rotated withrespect to the blood vessel or sliding/translated along the length ofthe blood vessel for a distance not equal to the pitch length, such ashalf the pitch length or one third of the pitch length) to imagedifferent spiral paths (imaged strip) along the blood vessel wall for amore complete scan. As previously discussed, it is preferred that theradius of the spiral be reduced prior to moving to a different positionin the vessel and then returned to the larger radius for imaging.Alternatively, multiple spiral imaging sheaths/imaging cores can beused.

FIGS. 6-8 illustrate an imaging assembly with a pre-formed spiralimaging sheath according to one embodiment of the present invention.FIG. 6 shows the spiral shape of the distal end of the imaging sheath(303) in the absence of external constraints, such as the presence ofthe guidewire or the ID of the vessel. The distal portion of the imagingsheath (with a guidewire lumen) is formed into a spiral. The imagingsheath is substantially transparent/translucent (or has a substantiallytransparent/translucent window on the outside of the spiral) to allowthe imaging core 301 to scan and image the wall of the blood vessel. Theproximal end of the optical fiber 307 can drive the imaging core (301)to rotate and move along the imaging sheath for a spiral scan.

In one embodiment, the spiral forming process, and/or the dimensionsand/or material stiffnesses of the imaging sheath (303) are manipulatedto ensure that imaging core lumen (313) has a natural tendency to be onthe outside of the spiral/nearest the vessel wall. For instance, thespiral can be formed by heat setting a thermoplastic sheath (303) into aspiral using a spiral (or straight) mandrel in the imaging core lumen(313) and another mandrel with a smaller spiral radius in the guidewirelumen (313). With sufficient stiffness and/or a great enough differencein spiral radius, the mandrels will force the guidewire lumen (311) tothe inside of the spiral and the imaging core lumen (303) to the outsideof the spiral (e.g., in a configuration similar to that illustrated inFIG. 12 but in absence of the guidewire 349).

In one embodiment, the guidewire lumen goes distal to the distal end ofthe sheath; and the guidewire lumen is open at the distal end of thesheath. A guidewire is used to deliver the imaging assembly to thedesired location in the vessel. After the guidewire is positioned acrossthe vessel region of interest, the imaging assembly (RX or OTW) istracked over the guidewire to the vessel region of interest. Theguidewires that have relatively short floppy distal ends (e.g., Ironmanseries of guidewires from Guidant Corporation) can work better than“normal” guidewires (e.g., Hi-Torque Floppy series of guidewires fromGuidant Corporation).

In one embodiment, an OCT imaging core/optical fiber is about0.004-0.005″ in OD and a guidewire for this application is about 0.014″in OD. Thus, the OD of the guidewire is roughly 3 times the OD of theoptical fiber/imaging core. Further, the OD of the imaging sheath in thecross-section view does not have to be circular. The OD of the imagingsheath in the cross-section view can be circular or noncircular, such asoval or egg shaped (e.g., as illustrated in FIG. 14).

FIG. 7 shows the imaging sheath (303) of FIG. 6 being temporarilystraightened by a guidewire (309). The guidewire (309) is of asubstantially straight shape, having a stiffness great enough in asection near its distal end so that when that section of the guidewire(309) is inserted into the spiral portion of the imaging sheath (303),the spiral portion of the imaging sheath (303) is substantiallystraightened. When the spiral portion of the imaging sheath (303) isstraightened, the overall diameter of the spiral of the imaging sheath(303) is reduced to allow the positioning of the imaging sheath (303).For example, the imaging sheath (303) can be inserted into the bloodvessel via a guide catheter and over the guidewire (309) and positionedacross a target location; or, the imaging sheath (303) may berepositioned after a scan. Once the imaging sheath (303) is at a desiredposition, the guidewire (309) can be withdrawn until only its distalfloppy end is in the spiral formed distal section of the imaging sheath(303) or pulled out of the spiral formed section of the imaging sheath(303) to allow the distal end of the imaging sheath (303) to come backto the spiral shape.

In one embodiment, when the straight guidewire is in the imaging sheath,as illustrated in FIG. 7, the overall structure of the distal portion isstill flexible enough to follow the guidewire and pass though turningpoints of a blood vessel (e.g., a vein or artery). Thus, the stiffnessof the guidewire and the stiffness of the imaging sheath are calibratedso that at least a section of the guidewire can straighten the spiral ofthe imaging sheath if that distal portion is in a straight section ofthe vessel and that distal portion can still bend when it encounters thevessel wall or bend with the guidewire to pass the turning points of theblood vessel to reach a target location without causing damage to theblood vessel wall. In one embodiment, the imaging sheath 303 may includea distal tapered tip/soft tip to aid it in following the guidewire intoposition in the curved vessel anatomy in the manner currently employedto aid in the atraumatic positioning of angioplasty catheters.

In one embodiment of the present invention, the pre-formed spiral radiusof the imaging sheath is larger than or approximately equal to theradius of the blood vessel at the target location so that, when theguidewire is withdrawn , the imaging sheath gently spirals against orvery close to the vessel wall.

FIG. 8 illustrates a cross section view along A-A′ in FIG. 7. Theimaging sheath is transparent at least for the back portion of thespiral to allow the passage of the light for OCT scanning. An imagingcore lumen (317) allows the optical fiber (307) to move longitudinallyand rotate within the imaging sheath (303). A guidewire lumen (311)allows the guidewire (309) to be inserted to straighten the spiralportion of the imaging sheath or withdrawn to allow the imaging sheathto form a spiral.

Alternatively, the imaging core and the guidewire may share the samedistal lumen. To reposition the distal portion of the imaging sheath ata target location, imaging core is withdrawn from the lumen and theguidewire is advanced into the lumen. To scan the vessel wall, theguidewire is withdrawn out of the lumen; and the imaging core isadvanced into the lumen (e.g., for an imaging pullback).

FIGS. 9-14 illustrate imaging assemblies with a pre-formed spiralguidewire according to embodiments of the present invention. FIG. 9shows a spiral guidewire (329) forcing the distal portion of an imagingsheath (323) into a spiral shape. The guidewire (329) is of a spiralshape in the distal portion, having a stiffness greater than thestiffness of the distal portion of the imaging sheath so that when theguidewire is inserted the distal portion of the imaging sheath (303) istemporarily forced into a spiral shape. When the imaging sheath ispositioned at the target location and forced into the spiral shape, animaging core (321) can be controlled though an optical fiber (327) toperform a spiral scanning. The imaging sheath is substantiallytransparent/translucent (or has a substantially transparent/translucentwindow on the back of the spiral) to allow the imaging core 301 to scanand image the wall of the blood vessel.

FIG. 10 shows the imaging sheath of FIG. 9 being in a substantiallystraight shape after the spiral guidewire is removed. When the distalportion of the imaging sheath (303) is straightened, the overalldiameter of the imaging sheath is reduced to allow the placement andrepositioning of the imaging sheath. For example, the imaging sheath canbe inserted into the blood vessel and positioned to a target location;or, the imaging sheath may be repositioned after a scan. The distal endof the imaging sheath (323) may include a fixed guidewire tip and/or abent end to aid in the subselection of the desired vessel branch.Alternatively, a conventional (straight) guidewire with various distalend configurations can be used in the guidewire lumen to guide theimaging sheath (323) to the target location in the conventional manner.Once the imaging sheath is at a desired location, the spiral guidewirecan be inserted into the imaging sheath to force the imaging sheath to aspiral shape.

In one embodiment of the present invention, the pre-formed spiral radiusof the guidewire is larger than or approximately equal to the radius ofthe blood vessel at the target location so that, when the guidewire isinserted, the imaging sheath gently spirals against (or close to) thevessel wall.

In one embodiment of the present invention, the stiffness of the spiralguidewire is smaller than a proximal portion of the imaging sheath suchthat when the spiral guidewire is in the proximal portion of the imagingsheath, the spiral guidewire is temporarily straightened/has less of aspiral. Thus, the spiral guidewire will only substantially bend thedistal portion of the imaging sheath into a spiral of the desiredradius, but not the proximal portion of the imaging sheath.Alternatively, the proximal portion of the imaging sheath is covered bya tube or a guide catheter, which temporarily straightens the spiralportion of the guidewire when the spiral portion of the guidewire is notinserted into the distal portion of the imaging sheath. The overallstiffness of the catheter assembly is calibrated so that the assembly isflexible enough to be delivered in a blood vessel without causing damageto the vessel wall.

FIG. 11 illustrates a cross section view along B-B′ in FIG. 9. Theimaging sheath (323) is substantially transparent/translucent for atleast a portion of the spiral to allow the passage of the light for OCTscanning. An imaging core lumen (333) allows the optical fiber (327) tomove longitudinally and rotate within the imaging sheath. A guidewirelumen (331) allows the guidewire (329) to be inserted to force thedistal portion of the imaging sheath into a spiral or withdrawn tostraighten the imaging sheath. Guidewire lumen (331) may also allow theimaging sheath (323) to follow a more conventional guidewire during theinitial positioning of the imaging sheath (323) in the vessel.

FIGS. 12-14 illustrate an embodiment in which the imaging core lumenspirals around the guidewire lumen. FIG. 12 shows a spiral guidewire(349) forcing the distal portion of an imaging sheath (343) into aspiral shape. The guidewire (349) is of a spiral shape in the distalportion, having a stiffness greater than the stiffness of the distalportion of the imaging sheath so that when the guidewire is inserted thedistal portion of the imaging sheath (343) is temporarily forced into aspiral shape.

FIG. 13 shows that the imaging core lumen (353) spirals around theguidewire lumen (351) when the spiral guidewire is not inserted into thedistal portion of the imaging sheath and the imaging sheath issubstantially straight. The imaging core lumen (353) spirals around theguidewire lumen (351) when the imaging sheath is substantially straight.Thus, when the spiral guidewire (349) is inserted into the guidewirelumen (351) in the distal portion, the imaging core lumen spiralsoutside the guidewire lumen, as illustrated in FIG. 12; and the spiralguidewire is inside the imaging core lumen so that the guidewire is notin the way between the imaging lumen and the vessel wall.

FIG. 14 illustrates a cross section view along C-C′ in FIG. 12. Theimaging sheath (343) is substantially transparent/translucent for atleast a portion of the spiral to allow the passage of the light for OCTscanning. An imaging core lumen (353) allows the optical fiber (347) tomove longitudinally and rotate within the imaging sheath (343). Aguidewire lumen (351) allows the guidewire (349) to be inserted to forcethe distal portion of the imaging sheath into a spiral or withdrawn tostraighten the imaging sheath. Guidewire lumen (351) may also allow theimaging sheath (343) to follow a more conventional guidewire during theinitial positioning of the imaging sheath (343) in the vessel.

FIGS. 15-17 illustrate an imaging assembly with a tube according to oneembodiment of the present invention. FIG. 15 illustrates a configurationin which an imaging sheath (361) is tightly wrapped in a spiral around aguide member (363). The distal end (360) of the imaging sheath (361) isfixed to the guide member (363); and the other end of the imaging sheath(361) is fixed to the tube (365). The guide member (363) is slidableinto the tube to reduce the distance between the two ends of the spiralimaging sheath (361). In FIG. 15, one end of the tube (365) is close tothe point Y (369) of the guide member. The spiral of the imaging sheath(363) is elongated so that the spiral radius of the imaging sheath (363)is small. Thus, the overall radius of the distal portion of the imagingassembly is small so that the distal portion of the imaging assembly canbe moved easily within an internal channel to a target position.

The distal end of the tube (365) is tapered so that there is no sharpedge to contact the vessel. The distal end (360) of the imaging sheath(361) is tapered to a larger OD, made of materials that have a highermodulus distally and/or contain a tapered stiffening device (a wire(s),braid, etc.) so the spiral will gradually curve away from the guidemember and not bend at a sharp angle when the spiral is expanded. Theproximal end of the imaging sheath connects to the distal end of thetube (365) in a similar fashion to avoid being bent at a sharp angle.The distal end of the guide member can be made moreconventional/atraumatic by extending it further distal of its connectionwith the imaging sheath. When the guide member is a guidewire, thedistal end of the guide member can be the short (short is preferred)floppy tip of the guidewire. When the guide member is a tube thataccommodates a guidewire in its ID, the distal end of the guide membercan be a soft tapered tip like those incorporated on angioplastycatheters. When the guide member is a shaft (no ID), the distal end ofthe guide member can be a soft tapered tip with a bent end and/or afixed guidewire.

The guide member (363) can be just a guidewire that can be pulled intoor pushed out of the tube (365). Alternatively, the guide member can bea tube or a catheter that accommodates the guidewire and that can bepulled into or pushed out of the tube (365) through pulling or pushingthe guidewire.

In FIG. 16, when the tube (365) is moved towards the distal end of theguide member, the guide member (363) slides into the tube (365). Thepoint Y (369) of the guide member is inside the tube (365); and thedistal end of the tube (365) is close to the point X (367) of the guidemember. Since the spiral of the imaging sheath (361) has one endattached to the distal end (360) of the guide member (363) and anotherto the tube (365), the spiral length of the imaging sheath (361) isreduced. Thus, the spiral radius of the imaging sheath (361) isincreased. The relative position of the guide member with respect to thetube can be adjusted to control the spiral length and spiral radius ofthe imaging sheath (361). The spiral radius can be adjusted so that thespiral of the imaging sheath gently contacts the vessel wall. Then, aspiral section of the vessel wall can be imaged with reduced signalblockage from blood in the vessel since the imaging sheath is broughtclose to the spiral section of the vessel wall.

Further, the tube can be rotated (371) with respect to the guide memberto change the number of spiral turns of the imaging sheath (363). Whenthe tube (365) is rotated with respect to the guide member (363) in thedirection as shown in FIG. 16 (and/or the guide member is rotated withrespect to the tube in the opposite direction), the number of spiralturns decreases, which causes the spiral to expand (e.g., increasing thespiral radius); when the tube (365) is rotated with respect to the guidemember (363) in the opposite direction, the number of spiral turnsincreases, which causes the spiral to shrink (e.g., decreasing thespiral radius).

In one embodiment of the present invention, the proximal end of theimaging assembly (the catheter assembly) contains a handle with markers(or indicators) that guide the operator in adjusting the spiral radiusof the distal end and/or prevents/limits excessive expanding forces,rotations and/or displacements from being applied to the spiral of theimaging sheath, which may cause damage to the imaging assembly and/orthe vessel wall. As a practical matter, observation of the imagesproduced during a pull back of the imaging core provides a reliablemeans to ensure that the spiral is near enough to the vessel wall. Ifthe imaging sheath is away from the vessel wall, the image produced willshow the separation of the imaging sheath from the vessel wall. Anytimethat the imaging sheath is too far from the vessel wall, the pull backmay be discontinued, the spiral adjusted to produce the desired vesselwall contact/proximity and then the imaging pull back may be resumed.

FIG. 17 illustrates a cross section view along D-D′ in FIG. 16. The tube(365) has a guide lumen (379) and an imaging lumen (373). The imaginglumen (379) connects to the imaging sheath to provide a continuouspassageway for the optical fiber (377) for the control of the imagingcore in the imaging sheath (361). The guide lumen (379) allows the guidemember (363) to slide into the tube to compress the spiral length theimaging sheath or slide out of the tube to extend the spiral length ofthe imaging sheath. The cross-section of tube (365) may be oval or moreegg-shaped and not circular, as shown, if desired.

Although FIGS. 16 and 17 illustrate the adjustment of the spiral lengthand the number of spiral turns through moving the tube, it is understoodthat it is the relative movement between the tube and the guide memberthat causes the adjustment of the spiral length and the number of spiralturns. The relative movement between the tube and the guide member canbe achieved through fixing the tube to move the guide member (e.g., withrespect to the vessel), or through fixing the guide member to move thetube (e.g., with respect to the vessel), or through moving both theguide member and the tube (e.g., with respect to the vessel) to causethe relative movement.

Further, in one embodiment, the imaging sheath is slidable within alumen in the tube while the guide member is fixed relative to the tubeto fix the spiral length. Advancing a length of imaging sheath throughthe lumen in the tube increases the length of the imaging sheath in thespiral for the given spiral pitch (e.g., at a given spiral length and agiven number of spiral turns) and thus increases the spiral radius;withdrawing a length of imaging sheath reduces the spiral radius. In oneembodiment, the guide member and the tube are fixed with respect to eachother to have a fixed spiral length and/or a fixed number of spiralturns; sliding the imaging sheath into or out of the tube adjusts thelength of the imaging sheath in the spiral to expand or collapse thespiral. In one embodiment, both the imaging sheath and the guide memberare slidable in their respective lumens. A proximal handle/controlmechanism can be used to control the spiral through controlling therelative positions of the imaging sheath, the guide member and/or thetube. The proximal relative longitudinal position of the guide memberwith respect to the tube can be controlled to adjust the spiral length;the proximal relative longitudinal position of the guide member and theimaging sheath can be controlled to adjust the spiral length; and theproximal relative rotation of the guide member with respect to the tubecan be controlled to adjust the number of spiral turns. Selectivelyadjusting the length of the imaging sheath in the spiral, the spirallength and the number of spiral turns can expand or collapse the spiral,as discussed above. In some implementations, the imaging sheath is freeto rotate at its proximal and/or distal end to relieve strains that maybe introduced when the tube is rotated relative to the guide member.

FIGS. 18-20 illustrate an imaging assembly on the distal end of acatheter (not shown) with a tendon according to one embodiment of thepresent invention. In FIG. 18, the tendon (407) is not in tension sothat the guide member (409) is substantially straight. The tendon lumen(403) spirals around the guide member (409) on one side; and the imagingsheath (401) spirals around the guide member (409) on the opposite sideof the tendon (407). The tendon (407) is preferably attached to thedistal end of the tendon lumen (403) wall, but is otherwise free to movewithin the tendon lumen (403). The optical fiber (405), a portion of theimaging core, in the imaging sheath (401) provides the light passagewayfor OCT imaging and its proximal portion provides the control over themovement of the imaging core for scanning.

FIG. 19 shows the tendon bending the imaging assembly when the tendon isin tension (pulled proximal relative to the rest of the assembly). Whenthe tendon is in tension, the guide member (409) and the imaging sheath(401) are bent into a spiral shape. The contraction force of the tendoncauses the tendon lumen (403) to stay at the inside of the spiral; andthe imaging sheath (401) is at the outside of the spiral. Thus, thetendon (407) and tendon lumen (403) are not in the way between theimaging sheath (401) and the spiral section of a vessel wall to beimaged.

FIG. 20 shows the cross section view along E-E′ in FIG. 18. Although thecross-section is shown to be oval, it is to be understood that thecross-section could be constructed as circular or in other shapes. Atleast the outside facing portions of the imaging sheath (401) (e.g. theportion of the assembly that accommodates the imaging core) istransparent or adequately translucent so that the light can be projectedfrom the imaging core to the vessel wall and scattered back to theimaging core through the imaging sheath (401). The imaging sheath (401)provides a passageway for the imaging core. The guidewire (415) is usedto provide the stiffness to the assembly so that the distal portion ofthe imaging assembly is substantially straight when the tendon is not intension. The guidewire may be slidable within a guidewire lumen of theguide member (409); alternatively, the guidewire may be integrated withthe imaging sheath (401) and the tendon lumen (403). The imaging sheath(401) and the tendon lumen (403) are on the opposite sides of the guidemember (409). When the tendon (407) is in tension, the tendon lumen(403) wall is compressed to reduce its length, which causes the bendingof the assembly into a spiral.

The longitudinal translation of the tendon (407) relative to the tendonlumen (403) wall or the tension force applied to the tendon can be usedto control the bending of the spiral. The greater the tension force orthe proximal translation of the tendon (407) applied, the smaller thespiral pitch may be. The spiral of the tendon lumen (403) wall aroundthe guide member (409) and the stiffness of the guide member (409) canbe designed so that when the assembly is bent under tendon (407) controlinto a spiral, the spiral gently contacts the vessel wall without anexcessive expanding force on the vessel wall. Note that only the imagingsection of the catheter assembly is described here, as the distal tipand proximal sections of the catheter may be of conventional angioplastyand deflection catheter designs, respectively. As before, in someembodiments, the guidewire lumen can be eliminated, at least from thedistal section of the catheter, when the catheter or imaging sheath isdesigned such that the imaging core and guidewire can replace each otherwithin the imaging sheath.

FIG. 21 shows an axial slice view of the imaging assembly when thetendon is not in tension. In FIG. 21, the guide member (409) issubstantially straight (see also FIG. 18) when the tendon is not intension. Since the imaging assembly has a small overall radius, there isa significant distance between the imaging sheath and the wall of theartery (421). The imaging sheath (401) and the tendon lumen (403) spiralaround the guide member (409). The blood between the artery wall and theimaging sheath may reduce the imaging capability and the image qualityof the OCT scan. In FIG. 21, only small length segments (the width ofthe view slice) of the imaging sheath (401) and the tendon lumen (403wall) are shown so that both segments of them can be seen clearly.

FIG. 22 shows an axial slice view of the imaging assembly when thetendon is in tension. In FIG. 22, the guide member (409) is bent into aspiral when the tendon is in tension (see also FIG. 19). The tendonlumen (403) is at the inside of the spiral; and the imaging sheath (401)is at the outside of the spiral, gently contacting the wall of theartery (421). Since the imaging assembly spirals into contact with theartery, the imaging sheath (401) is very close to a spiral section ofthe wall of the artery (421). The blood in the artery will not reducethe imaging capability and the image quality of the OCT scan of thespiral section of the artery wall. Also, the spiral-shaped imagingassembly does not severely block the blood flow in the artery.

The assembly of FIGS. 18-22 can be used for OCT imaging, where theimaging sheath (e.g., 401) can be used to accommodate the imaging coreof an OCT imaging system. Similar assemblies can also be used forphotodynamic therapy to the vessel wall and/or to perform the opticaltemperature measurement of the vessel wall. The assembly can be deformedinto a spiral using the tendon (e.g., 407) to bring the sheath (e.g.,401) for the core of photodynamic therapy or optical temperaturemeasurement into gentle contact, or closer to, a section of the vesselwall.

FIGS. 23-26 illustrate an imaging assembly with a spiral balloonaccording to one embodiment of the present invention. FIG. 23illustrates a distal portion when the spiral balloon (441) is deflated;and FIG. 24 illustrates a distal portion when the spiral balloon (441)is inflated. The imaging sheath (443) spirals on the back of the spiralballoon (the outside of the spiral balloon). When the spiral balloon isdeflated, the overall diameter of the distal portion is small, allowingthe free movement of the distal portion in an internal channel. When thespiral balloon is inflated, the backside of the spiral balloon pushesthe imaging sheath toward a spiral section of the internal channel. Theguide member (447) has a stiffness to remain substantially straightbefore and after the spiral balloon is inflated but is flexible enoughto traverse in the internal channel. Thus, even when the spiral balloonis inflated, the distal portion of the assembly leaves at least a spiralportion of the channel unblocked so that fluid (e.g., blood) can stillflow in the channel.

FIG. 25 illustrates a cross section view along F-F in FIG. 23 where thespiral balloon is deflated. FIG. 26 illustrates a cross section viewalong G-G′ in FIG. 24 where the spiral balloon is inflated. The guidemember at or near in the center of the spiral regardless whether thespiral balloon is inflated or deflated. Thus, the imaging sheath is awayfrom the wall of the internal channel (e.g., an artery) and close to theguide member when the balloon is deflated; and the imaging sheath isaway from the guide member and close to (or gently touching) a spiralsection of the wall when the balloon is inflated.

When the spiral balloon is inflated, the outside of the spiral balloonis stretched. In one embodiment, the imaging sheath is flexible andfixedly attached to the spiral balloon. Thus, when the spiral balloon isinflated, the imaging sheath is stretched together with the backside ofthe spiral balloon. Alternatively, the imaging sheath is movablerelative to the imaging sheath. For example, the spiral balloon has alumen housing the imaging sheath; the imaging sheath is slidable withrespect to the spiral balloon in the lumen. Thus, when spiral balloon isinflated, the imaging sheath expands to have a spiral radius accordingto the backside of the spiral balloon and slides within the lumen toavoid being stretched. The distal end of the imaging sheath may be freeto move; thus, when the spiral balloon is inflated, the distal end ofthe imaging sheath moves proximal to reduce the spiral length to avoidbeing stretched. Alternatively, the distal end of the imaging sheath maybe fixed to the spiral balloon and the guide member; the proximal end ofthe imaging sheath is slidable with respect to a tube; thus, when thespiral balloon is inflated, a portion of the imaging sheath slides outof the tube to increase the length of the part of the imaging sheaththat spirals on the back of the spiral balloon (due to the increase inspiral radius). In one embodiment, the balloon has a small attachment tothe imaging sheath. Alternatively, the balloon may be attached to thesheath through a loop (not shown in FIGS. 25 and 26). Through suchattachment arrangements, the sheath is prevented from beingcrushed/deformed when the balloon is inflated. Deforming the imagingsheath may make the movement of the imaging core within it difficult.Alternatively, the movement of the imaging sheath in radial andcircumferential directions may be constrained to the spiral balloonalong a number of points on the backside of the spiral balloon; and theimaging sheath is slidable along the spiral of the backside of theballoon.

FIGS. 27-30 illustrate an imaging assembly with an elastic or compliantballoon according to one embodiment of the present invention. FIG. 27illustrates a distal portion when the balloon (461) is deflated; andFIG. 28 illustrates a distal portion when the balloon (461) is inflated.The balloon (461) encloses a distal section of the guide member (467);and the imaging sheath (463) spirals outside the balloon. When theballoon is deflated, the overall diameter of the distal portion isreduced for positioning or repositioning the distal portion in aninternal channel. When the balloon is inflated, the inflated balloonexpands the spiral radius of imaging sheath so that the imaging sheathis close to or in contact with a spiral section of the internal channel.The guide member (467) has a stiffness to remain substantially straightbut is flexible enough to traverse in the internal channel.

An elastic or compliant balloon may almost completely block the internalchannel when the balloon is fully inflated. In one embodiment of thepresent invention, the guide member (467) includes a reperfusioncatheter chassis. Although the elastic balloon causes more blockage ofthe blood flow in the vessel compared to a spiral balloon, thereperfusion lumen of the catheter chassis provides a channel for bloodflow in the vessel. Alternatively, to avoid blockage of the flow in thechannel (e.g., blood flow in the artery), the balloon may be inflatedonly to a degree such that the expanded spiral radius of the imagingsheath spiral is close to the radius of the channel; thus, the imagingsheath is close enough (e.g., within the imaging radius) to a spiralsection of the wall; and the balloon would not completely block theinternal channel. For example, the balloon may be inflated so that thespiral radius of the imaging sheath is still smaller than the radius ofthe internal channel. Thus, the flow may go through the spiral aroundthe balloon and outside the imaging sheath.

FIG. 29 illustrates a cross section view along H-H′ in FIG. 27 where theballoon is deflated. FIG. 30 illustrates a cross section view along I-I′in FIG. 28 where the balloon is inflated. The guide member is at or nearthe center of the spiral of the imaging sheath. Thus, the imaging sheathshrinks toward the center to reduce the overall radius of the assemblywhen the balloon is deflated and expands to be substantially uniformlyclose a spiral section of the wall when the balloon is inflated. FIGS.29 and 30 also illustrate a loop/attachment area (469) which constrainsthe imaging sheath (463) to the outer surface of the balloon (461). Theloop/attachment area (469) does not constrain the imaging sheath (463)in the longitudinal direction so that, when the balloon is deflated orinflated, the imaging sheath is not compressed or stretchedlongitudinally. The loop/attachment area (469) can be applied only atseveral locations along the imaging sheath. The loop/attachment area canalso extend in along the imaging sheath to define a lumen.

The imaging sheath may be flexible so that the imaging sheath stretcheswith the outside of the balloon when the balloon is inflated.Alternatively, the imaging sheath may be slidable with respect to theimaging sheath (e.g., in a lumen attached to the balloon or constrainedalong a spiral on the outside of the balloon). Alternatively, theimaging sheath is pre-formed with a small spiral radius so that theimaging sheath wraps around the balloon. When the balloon is inflated,the balloon temporarily expands the imaging sheath. When the balloon isdeflated, the imaging sheath springs back to the small spiral radius toremain wrapped on the balloon.

In one embodiment of the present invention, when the balloon (441 or461) is inflated or deflated, the spiral pitch for the imaging sheathremains substantially the same. When the spiral pitch is fixed, thelength of the imaging sheath in the spiral changes as the spiral radiuschanges. In one embodiment, the imaging sheath is attached at or nearthe distal end of the balloon's major Outside Diameter (OD) and theimaging sheath is designed to accommodate the length changes caused bythe balloon's inflation. In one implementation, the imaging sheath hasone or more telescoping sections; loops, a channel, or segments ofchannels are used to loosely constrain the imaging sheath to theballoon; alternatively, the imaging sheath is fixedly attached to theballoon OD at one or more locations between telescoping sections of theimaging sheath. In one implementation, the imaging sheath is constrainedalong a spiral path outside balloon (e.g., using a number of loops, or atransparent/translucent channel, or a number of segments of channels);the imaging sheath is slidable along the spiral path to adjust thelength of the imaging sheath in the spiral over the balloon. Forexample, when the balloon is inflated, a length of the imaging sheath ispulled into the spiral located outside the balloon by the ballooninflating force. When the balloon is deflated, the length of the imagingsheath can be withdrawn at the proximal end (or pushed out from thespiral by the deflating balloon) to wrap the imaging sheath tightly onthe balloon. Alternatively, the imaging sheath is made of an elasticmaterial, which can stretch and shrink back to conform to the OD of theballoon.

FIGS. 31-38 illustrate an imaging assembly with a plurality of imagingsheaths according to one embodiment of the present invention. In FIG.31, a guidewire (507) is slidable and rotatable with respect to a tube(503). Two imaging sheaths spiral around the guidewire that extendsoutside the tube (503). The distal ends of the imaging sheath are fixedto the distal end (510) of the guidewire. The proximal ends of theimaging sheath are fixed to the tube (503). The tube contains lumensconnected to the imaging sheath to provide continuous passageways forthe optical fibers (505) of the OCT system.

When the guidewire (507) fully extends outside the tube, the spirallength of the imaging sheaths is stretched to fully reduce the spiralradius. Thus, the imaging sheaths (501) wrap around the guidewire (507)as illustrated in FIG. 31.

When the guidewire (507) slides into the tube, the spiral length of theimaging sheaths is shortened to increase the spiral radius. Thus, thespirals of the imaging sheaths (501) expand in radius, as illustrated inFIG. 32. Further, the guidewire can rotate with respect to the tube tochange the number of spiral turns and thus the spiral radius. FIG. 33illustrates the spirals with the reduced number of spiral turns and theincreased spiral radius, after the tube (503) is rotated with respect tothe guidewire (507) from the position in FIG. 32. In practice, the tubeis typically not rotated with respect to the vessel; the guidewire isrotated with respect to the vessel so that the tube and the guidewirerotate with respect to each other. The relative rotation between thetube and the guidewire adjusts the number of spiral turns. Similarly,the relative longitudinal translation between the tube and the guidewireadjusts the spiral length. One may hold the tube still with respect tothe vessel and move the guidewire with respect to the tube to adjust thespiral length and the number of spiral turns, or hold the guidewirestill with respect to the vessel and move the tube with respect to theguidewire, or move both the guidewire and the tube with respect to thevessel to cause relative movement between the guidewire and the tube.Further, in one embodiment, the imaging sheaths can slide in the tube toadjust the length of imaging sheaths in the spirals (e.g., throughadvancing or withdrawing a length of the imaging sheaths into the tubewhile holding the guidewire and the tube still). Selectively adjustingthe length of the imaging sheath in the spiral, the spiral length andthe number of spiral turns can expand or collapse the spiral.

The example of FIGS. 31-33 illustrates an embodiment in which eachimaging sheath houses its own imaging core and each of the imaging corehas an optical fiber (505) attached and connected to the proximal end ofthe assembly. Each of the imaging cores can scan a spiral section of thewall close to the corresponding imaging sheath. Alternatively, a singleimaging core may be inserted into one of the imaging sheath for scanninga spiral section of the wall close to the imaging sheath in which theimaging core is housed. Different spiral sections of the wall can bescanned through inserting into and sliding out from the imaging sheathsone after another.

The OCT images of the spiral sections of the wall can be combined toprovide a more complete view of the wall. When the spiral sectionsoverlap, a 360-degree of circumferential image of the wall can beconstructed.

Although the example of FIGS. 31-38 illustrates only two imagingsheaths, from this description it will be apparent to one skilled in theart that a plurality of imaging sheaths (e.g., three or more) can beused in general. It will also be apparent to one skilled in the art thatthe embodiments described relative to FIGS. 15 through 17 and 23 through30 may be similarly modified to contain multiple imaging sheaths.

FIGS. 34-36 illustrate cross section views along M-M′, N-N′ and O-O′ inFIG. 31, where the guidewire fully extends outside the tube (503) tocollapse the spirals of the imaging sheaths onto the guidewire (507).The spiral radius d₁ (511) is small in FIG. 35, since the imagingsheaths wrapping tightly around the guidewire (507). In the small radiusconfiguration, the distal portion of the imaging assembly can beinserted into and moved along an internal channel (e.g., an artery) toreach a target location. FIGS. 34-36 show the different positions of theimaging sheaths (501) relative to the guidewire (507) at different crosssections according to the spirals.

FIG. 37 illustrates a cross section view along P-P′ in FIG. 32, wherethe guidewire slides into the tube (503) to expand the spirals of theimaging sheaths. The spiral radius d₂ (513) is larger than d₁ (511) sothat the imaging sheaths are close to the spiral sections of the wall ofthe internal channel.

FIG. 38 illustrates a cross section view along Q-Q′ in FIG. 33, wherethe guidewire has been rotated to reduce the number of spiral turns ofthe imaging sheath and expand the spirals of the imaging sheaths. Thespiral radius d₃ (515) is larger than d₂ (513) so that the imagingsheaths are moved closer to the wall of the internal channel (or togently contact the wall).

FIGS. 39-42 illustrate an imaging assembly with a spiral ballooncovering the imaging sheath according to one embodiment of the presentinvention. In FIG. 39, the spiral balloon is deflated so that theoverall radius of the distal portion of the assembly is small. In FIG.40, the spiral balloon is inflated. The imaging sheath spirals aroundthe guide member (537) regardless whether the spiral balloon is inflatedor not. When the spiral balloon is inflated, the balloon pushes theblood in the vessel out of the region between the spiral imaging sheath(531) and a spiral section of the vessel wall so that the flow of theblood in the vessel is mainly in the region outside the light pathbetween the imaging sheath and the vessel wall. At least the portion ofthe spiral balloon between the vessel wall and the imaging sheath istransparent or adequately translucent. The spiral balloon allows bloodflow even after the balloon is fully inflated. The spiral radius of theimaging sheath does not change. The inflated spiral balloon reduces thethickness of the layer of blood between the imaging sheath and thevessel wall to that smaller than the imaging depth so that the vesselwall can be clearly scan imaged.

FIG. 41 illustrates a cross section view along R-R′ in FIG. 39. Thespiral balloon (533) covers the imaging sheath (531). When the balloonis deflated, the overall radius of the distal portion is small so thatthe distal portion of the assembly can be moved to a target location inthe blood vessel. In one embodiment, deflated balloons are folded (notshown in FIGS. 39 and 41). Thus, the balloon is not significantlystretched (a non-compliant balloon) or significantly stretched (acompliant balloon) when fully inflated as in FIGS. 40 and 42.Alternatively, elastic balloons that are fully elastic over the range ofuse can be used (as shown in FIGS. 39-42).

FIG. 42 illustrates a cross section view along S-S′ in FIG. 40. Thespiral balloon (533) expands to expel the blood from a region betweenthe imaging sheath (531) and a spiral section of the vessel well toreduce or eliminate the blood effect. The spiral radius of the imagingsheath remains the same; and the shape and the position of the spiral ofthe imaging sheath relative to the guide member (537) is not changed.

In one embodiment, the imaging sheath is integrated with the guidemember. After the imaging of a spiral section of the vessel wall, thespiral balloon is deflated; and the distal portion is repositioned forthe imaging of a different spiral section of the vessel wall (e.g., forthe same segment of the vessel or a different segment of the vessel).For example, the guide member may be moved along the vessel for adistance (e.g., a half or one third of the spiral pitch) for the imagingof a different spiral section; alternatively, the guide member may berotated (e.g., for 60 or 90 degrees) for the imaging of a differentspiral section. Alternatively, the guide member may include a guidewireand a lumen housing the guidewire. The imaging sheath is attached toguide member so that when the guide member rotates and/or slides withrespect to the guidewire, the imaging sheath can be repositioned for theimaging of a different spiral section.

FIGS. 43-46 illustrate an imaging assembly with a straight imagingsheath enclosed in a spiral balloon according to one embodiment of thepresent invention. In FIG. 43, a transparent or adequately translucentspiral balloon (533) covers a spiral portion of the imaging sheath(531). The spiral balloon spirals around the imaging sheath to cover aspiral portion of the imaging sheath. The imaging sheath and the spiralballoon are connected to the distal end of a catheter (541), whichincludes an air or fluid passageway (543) for inflating or deflating theballoon and a fiber lumen (545) as a passageway for the optical fiber(535) which is a part of the imaging core in the imaging sheath (531).In one embodiment, deflated balloons are folded (not shown in FIGS. 43and 45). Thus, the balloon is not significantly stretched (anon-compliant balloon) or significantly stretched (a compliant balloon)when fully inflated as in FIGS. 44 and 46. Alternatively, elasticballoons that are fully elastic over the range of use can be used (asshown in FIGS. 43-46).

FIG. 44 shows the spiral balloon clearing a spiral region outside theimaging sheath to reduce or eliminate the blood effect for the OCTimaging of a spiral portion of the wall of the blood vessel. After thespiral balloon is inflated to gently contact or move closer to a spiralsection of the vessel wall, the beam from the imaging core in theimaging sheath can be projected from within the balloon, through theballoon onto a spiral section of the vessel wall without having to passa significant layer of blood. Thus, the blood effect on OCT imaging forthe spiral section of vessel wall can be eliminated or reduced toacceptable levels.

FIG. 45 illustrates a cross section view along T-T′ in FIG. 43. Thespiral balloon (533) covers a spiral section of the imaging sheath(531). When the balloon is deflated, the overall radius of the distalportion is small so that the distal portion can be positioned orrepositioned in the blood vessel.

FIG. 46 illustrates a cross section view along U-U′ in FIG. 44. Thespiral balloon (533) expands to push the blood from a region between theimaging sheath (531) and a spiral section of the vessel well to reduceor eliminate the blood effect. The imaging sheath remains substantiallystraight when the spiral is inflated. The inflated spiral balloonoccupies only a portion of the cross section of the vessel (e.g., aquarter to half of the cross section area of the vessel). Thus, theinflated spiral balloon does not block the blood flow in the vessel.

In one embodiment, the spiral balloon (533) is rotatable about and/orslidable along the imaging sheath (e.g., the spiral balloon is mountedon a transparent or adequately translucent tube which is outside theimaging sheath and movable with respect to the imaging sheath). Thus,after scanning a spiral section of the vessel wall, the spiral ballooncan be deflated, repositioned with respect to the imaging sheath, andinflated again for the scanning of a different spiral section.

FIGS. 47-50 illustrate an imaging assembly with a plurality of tendonson a portion of the assembly to reduce bending according to oneembodiment of the present invention. FIG. 47 illustrates a transitionsection of the imaging assembly. The distal portion of the imagingassembly includes an imaging sheath (551) and a tendon lumen wall (553)spiraling on the opposite sides of a guide member (557). The tendon(565) is attached to the distal end of the imaging assembly or tendonlumen wall (553). When the tendon enclosed within the tendon lumen wall(553) is in tension, the tendon bends the distal portion into a spiral,as illustrated in FIGS. 18-20. However, in the proximal portion of theassembly, it is desirable to reduce the bending of the assembly so thatthe assembly remains substantially straight even when the tension forceis applied to the tendon enclosed within the tendon lumen wall (553) ofthe distal portion; this proximal portion of the assembly bendsaccording to the turns of the vessel, not the tension force applied tobend the distal portion of the assembly.

In one embodiment of the present invention, to reduce or eliminate thebending moment caused by the tension force, a transition portion (569)is used to connect a plurality of tendons to the tendon enclosed withinthe tendon lumen wall (553) of the distal portion. After the transitionportion (e.g., near the cross section L-L′), the plurality of tendonsare distributed around the outside of the assembly so that the resultingtension forces in the tendons cause a small or no net bending moment forthe assembly. For example, when two tendons are used in the crosssection L-L′, the tendons (565 and 567) can be placed to balance thebending moments resulting from the tension forces and cause little or nobending moment at the cross section of the assembly. To apply equalforces on the tendons (565 and 567), a pulley as shown in FIGS. 51 and52 can be used.

Although the example of FIGS. 47-50 shows the use of two tendons toreduce or eliminate the bending moment on a portion of the assembly, itis understood that a plurality of tendons can be distributed outside theassembly to reduce or eliminate the net bending moment produced by thetension forces. Further, the tendons may further merge to form acircular shell round the assembly.

FIG. 48 shows a cross section view along J-J′ in FIG. 47. Near the crosssection along J-J′ in FIG. 47, the tendon lumen wall (553) and imagingsheath (551) spiral around the guide member (557). The tendon lumen wall(553) is on the opposite side of the imaging sheath (551). When atension force is applied on the tendon (555), the tension force of thetendon causes a bending moment to bend the distal portion of theassembly into a spiral.

FIG. 49 shows a cross section view along K-K′ in FIG. 47. Near the crosssection along K-K′ in FIG. 47, the tendon and the tendon lumen starts tosplit into two. For example, the tendon (555) in the portion near thecross section of J-J′ splits into the two tendons (565 and 567). Each ofthe tendon (565 and 567) provides half of the tension force required bythe tendon (555) in the distal portion of the assembly.

Between cross section K-K′ and L-L′, the tendons (565 and 567) arerouted to positions to reduce or eliminate the overall bending momentcaused by the tension force.

FIG. 50 shows a cross section view along L-L′ in FIG. 47. Near the crosssection along L-L′ in FIG. 47, the tendons (565 and 567) are housed inseparate lumens (566 and 568). The tendons (565 and 567) are arranged onthe opposite sides of the geometric or bending center of this portion ofthe assembly so that when equal tension forces are applied on thetendons (565 and 567), the resulting net bending moment on the crosssection is significantly reduced or completely eliminated.

Typically, the tension forces in the tendons are generated throughpulling the tendons relative to the tendons' lumen walls. While thetendons are in tension, the tendons lumen walls and the part of theassembly that it is coupled to (e.g., fixedly attached to) are incompression. The resultant of the compression forces that counterbalancethe tension forces in the tendons is typically centered at or near thegeometric center of the cross section of the assembly (e.g., when a sametype of material is used to form the tendon lumen walls in a symmetricdesign and the part of the assembly that is fixedly coupled to thetendon lumen walls). Thus, when the resultant of the tendon tensionforces is also centered at the geometric center of the cross section ofthe assembly, there will be no net bending moment generated from pullingthe tendons.

Thus, the distribution of the tendons on the rest of the assemblysignificantly reduces or completely eliminates the bending moment causedby the tension forces of the tendons. When the tendons at the proximalend of the assembly are pulled to put the tendon in the distal end intension, which bends the distal portion of the assembly into a spiral,the rest of the assembly is still substantially straight.

FIGS. 51-52 illustrate an assembly to balance the forces in two tendonsfor an imaging assembly according to one embodiment of the presentinvention. FIG. 51 shows a side view of a pulley (571) used to balancethe forces on the tendons (565 and 567) at the proximal end of animaging assembly for bending a distal portion of the imaging assembly.When a force F (573) is applied on the axis of the pulley (571), thepulley (571) distributes equal tension forces on the tendons (565 and567). FIG. 52 shows a top view of the pulley (571) balancing the forcesfor the tendons (565 and 567). The pulley (571) can rotate freely aboutthe axis (573). When the forces applied on the tendons (565 and 567) arenot equal, the unbalanced forces cause the pulley to rotate until thetension forces in the tendons are equal.

FIGS. 51-52 illustrate an example of using a pulley to directly balancethe forces in the tendons. Alternatively, the forces in the tendons canbe substantially balanced indirectly through the control of the amountof stretch in the tendons. For example, when the tendons have the samecross section area and the same length when not in tension, the sameamount of stretch applied on the tendons generates the same amount oftension forces in the tendons. Thus, a device can be used at theproximal end of an imaging assembly to provide equal amount of stretchfor each of the tendons to substantially balance the forces in thetendons and to reduce or eliminate the bending moment caused by theforces in the tendons.

Further details about a tendon deflection system with reduced bendingmoment can be found in a co-pending U.S. patent application Ser. No.10/255,034, filed Sep. 25, 2002, which is incorporated here byreference.

FIG. 53 illustrates a catheter assembly according to one embodiment ofthe present invention. The distal portion of the assembly (610) includesa guidewire (607) and an imaging sheath (601) spiraling around theguidewire (607). The imaging sheath (607) is attached to the guidewire(607) at the distal end, as illustrated in FIG. 15. Thus, when theguidewire is pulled, the spiral of the imaging sheath (601) iscompressed in length and expanded in diameter, as illustrated in FIG.16. When the guidewire extends out, the spiral of the imaging sheathcollapse around the guidewire, as illustrated in FIG. 15.

A portion (620) that is close to the distal portion (610) may include aballoon (603). The balloon (603) may be inflated or deflated through anopening (615) to an air or fluid passageway 609. An opening (613)connected to the saline passageway (611) can be used to inject saline.This portion may further include one or more needles (not shown in FIG.53) for delivering therapeutic substances to the blood vessel wall(e.g., according to the diagnosis based on the OCT imaging using theimaging sheath (601)). The balloon may be used to positioning theneedle(s) for delivering therapeutic substances. After the imaging ofthe internal wall of an artery for the detection of a vulnerable plaque,the operator can push the guidewire so that the radius of the spiral ofthe imaging sheath shrinks and the imaging sheath wraps around theguidewire; then, the operator may advance this portion (620) to thelocation of the detected vulnerable plaque for treatment.

The proximal portion (630) is can be manipulated outside a body tooperate the distal portion (601) that is inserted into the artery forOCT scanning. For example, the guidewire (607) at the proximal portion(630) can be pulled to cause the spiral of the imaging sheath at thedistal portion to expand and gently contact the vessel wall; and theguidewire (607) can be pushed at the proximal portion (630) to cause thespiral of the imaging sheath at the distal portion to collapse forrepositioning. The optical fiber (605) is connected to the imaging headin the imaging sheath through a passageway in the catheter and theimaging sheath. The optical fiber (605), which may be wrapped within asleeve, can be pulled (or pushed) and rotated to perform OCT scan usingthe imaging head in the imaging sheath in the distal portion. Air orfluid can be applied at the air or fluid passageway (609) at theproximal portion to inflate the balloon (603); and, saline can beapplied at the saline passageway to inject saline into the artery.

FIG. 53 illustrates a particular type of distal portion with a guidewireand a spiral imaging sheath. Other types of distal portions for animaging assembly, such as those illustrated in FIGS. 6-46, can also beused. From this description, a person skilled in the art can envisionvarious different combinations of different portions of the imagingassembly for OCT imaging and for therapeutic operations. Embodiments ofthe present invention are not limited to the particular combinationsillustrated in the Figures.

From this description, it is understood that various assembliesaccording to embodiments of present invention, as illustrated in FIGS.6-53 can be used for OCT imaging as well as photodynamic therapy to thevessel wall and/or to perform the optical temperature measurement of thevessel wall. The imaging sheath can be used to host the core for OCTimaging, for photodynamic therapy, and/or optical temperaturemeasurement.

FIG. 54 illustrates a method of using an imaging assembly according toone embodiment of the present invention. After collapsing an imagingsheath of an OCT system into a small radius configuration (e.g., to besubstantially straight or to spiral with a small radius) (701), anoperator inserts the imaging sheath into a body lumen (e.g., artery)while the imaging sheath remains in the small radius configuration(703). For example, the operator may insert the straight guidewire intoa spiral imaging sheath to straighten the imaging sheath as illustratedin FIG. 7, or pull the spiral guidewire out of the straight imagingsheath as illustrated in FIG. 10 or FIG. 13, or extend or push the guidemember out of the tube to collapse the spiral imaging sheath around theguide member as illustrated in FIG. 15, or relax the tendon tosubstantially straighten the imaging sheath as illustrated in FIG. 18,or deflate the balloon in the distal portion as illustrated in FIG. 23,27, 39 or 43. The portion of the imaging assemble being inserted intothe body lumen is flexible enough to be able to follow the gentle turnsof the body lumen without causing damage to the body lumen. The distalportion of the imaging assembly may have radiopaque markers (and/or OCTdetectable features) so that the imaging sheath can be guided into atarget location for OCT scanning.

After expanding the imaging sheath into a large radius configuration(e.g., to spiral with a large radius to gently contact or move closer tothe vessel wall along the imaging sheath) without substantially blockingthe body lumen (e.g., without blocking the blood flow in artery) (705),the operator performs an OCT scan using an OCT imaging core in theimaging sheath (e.g., to detect Vulnerable Plaque in coronary withoutflushing) (707). For example, the operator may pull the straightguidewire out of the spiral imaging sheath to cause the imaging sheathto spiral in the blood vessel as illustrated in FIG. 6, or insert aspiral guidewire to force the imaging sheath to spiral as illustrated inFIG. 9 or FIG. 12, or pull the guide member into the tube or rotate theguide member with respect to the tube to expand the imaging sheathspiral as illustrated in FIG. 16, or pull the tendon to bend the imagingsheath into a spiral as illustrated in FIG. 19, or inflate a balloon inthe distal portion as illustrated in FIG. 24, 28, 40, or 44. In general,any OCT imaging techniques can be used with the present invention.Further, imaging techniques other than OCT may also be used with thepresent invention, especially those that may degrade in the imagingquality in the presence of a thick layer of blood between in the vesseland the imaging sheath. Further, the catheter system can also be usedfor optical temperature sensing through receiving lights at the coreand/or for photodynamic therapy through delivering an optical beam fromthe core.

After collapsing the imaging sheath of the OCT system into the smallradius configuration (709), the operator retreats the imaging sheathfrom a body lumen (711) or repositions it in the body lumen for furtherimaging. Alternatively, the operator may further advance a needleportion of the catheter assembly to provide treatments for a portion ofthe imaged section of the vessel wall according to the diagnosis basedon the OCT imaging. The OCT imaging may also be used to guide the needleportion into a diseased portion of the vessel for treatment.Alternatively, the operator may reposition the imaging sheath for thescan of different portions of the vessel wall.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof It will be evidentthat various modifications may be made thereto without departing fromthe broader spirit and scope of the invention as set forth in thefollowing claims. The specification and drawings are, accordingly, to beregarded in an illustrative sense rather than a restrictive sense.

What is claimed is:
 1. An elongated assembly, comprising: a proximalportion; and a distal portion, the distal portion to be inserted into ablood vessel, the distal portion controllable through the proximalportion, the distal portion comprising: an elongated sheath, theelongated sheath housing a core capable of emitting an optical beam forimaging, the core movable along the sheath; a guide structure coupledwith the elongated sheath, the guide structure being controllablethrough the proximal portion to increase an overall diameter of thedistal portion from a first overall diameter of a first configuration toa second overall diameter of a second configuration, in the secondconfiguration the elongated sheath having a substantially spiral shapehaving a plurality of spirals, the sheath being made of a material thatis substantially transparent or translucent on an outside of thespirals, wherein the guide structure, through lateral movement in alumen of the elongated sheath, cause the sheath to take the spiralshape; and a control mechanism to facilitate movement of the corethrough the spirals while imaging, wherein the spiral shape has apre-shaped spiral radius having a pitch length of the spirals that isselected to be less than ten times a known radius of the vessel.
 2. Theassembly of claim 1, wherein the core is capable of projecting lightthrough the material and into a portion of the vessel and receivinglight from the portion of the vessel and through the materialsufficiently to use the received light to form an image of an imagedepth of a vessel wall or vulnerable plaque at the portion of thevessel.
 3. The assembly of claim 2, wherein the image depth one ofcomprises a thickness of two millimeters of tissue of the vessel wall,or is sufficient to identify the presence of a diseased region on thevessel wall.
 4. The assembly of claim 1, wherein one of (1) the distalportion has a pre-shaped spiral shape that includes the pre-shapedspiral radius having the pitch length and the guide structure is a stiffguidewire with a straight shape; or (2) the distal portion has astraight shape and the guidewire has a stiff pre-shaped spiral shapethat includes the pre-shaped spiral radius having the pitch length. 5.The assembly of claim 1, further comprising one of a guide wire, aballoon, a tube, or a tendon controllable through the proximal portionto increase an overall diameter of the distal portion from the firstoverall diameter to the second overall diameter.
 6. The assembly ofclaim 1, wherein a pitch length of the spiral shape and an imaging depthof the core are sufficient to identify vulnerable plaque on the bloodvessel.
 7. The assembly of claim 1, wherein, when the elongated sheathis in the substantially spiral shape: movement of the core along theelongated sheath does not change the substantially spiral shape of theelongated sheath; and the core is capable to scan the vessel along aspiral path on the vessel.
 8. The assembly of claim 1, wherein the pitchlength of the spiral shape is one of less than five times an imagingdepth of the core, or less than a size of a significant vulnerableplaque on a blood vessel plus two times an imaging depth of the core. 9.The assembly of claim 1, wherein in the second configuration a diameterof the spiral shape is substantially equal to a diameter of the vessel.10. The assembly of claim 1, wherein the distal portion has a stiffnessto be of a spiral shape in absence of external constrains; wherein astraight guidewire is insertable into the distal portion to straightenthe distal portion into the first configuration, and wherein thestraight guidewire is insertable into the elongated sheath in the distalportion to straighten the distal portion into the first configuration.11. An assembly, comprising: a sheath having a spiral shape having aplurality of spirals to be disposed along a blood vessel, the sheathbeing made of a material that is substantially transparent ortranslucent on an outside of the spiral, the sheath housing a corecapable of at least one of: projecting an optical beam onto a portion ofthe vessel and receiving a light from a portion of the vessel, the corebeing movable along the sheath to scan at least a spiral portion of thevessel, wherein the guide structure, through lateral movement in a lumenof the elongated sheath, cause the sheath to take the spiral shape; anda control mechanism to facilitate movement of the core through thespirals while imaging, wherein the spiral shape has a pre-shaped spiralradius having a pitch length of the spirals that is selected to be lessthan ten times a known radius of the vessel.
 12. The assembly of claim11, wherein the sheath has a guide member lumen; and a diameter of thespiral shape is substantially equal to the diameter of the vessel, andwherein the sheath is capable of being straightened in the vessel when aguide member is inserted into the guide member lumen.
 13. The assemblyof claim 11, wherein the core is capable of projecting light through thematerial and into a portion of the vessel and receiving light from theportion of the vessel and through the material sufficiently to use thereceived light to form an image of an image depth of a vessel wall orvulnerable plaque at the portion of the vessel.
 14. The assembly ofclaim 13, wherein the image depth one of comprises a thickness of twomillimeters of tissue of the vessel wall, or is sufficient to identifythe presence of a diseased region on the vessel wall.
 15. The assemblyof claim 11, wherein one of (1) the distal portion has a pre-shapedspiral shape that includes the pre-shaped spiral radius having the pitchlength and the guide structure is a stiff guidewire with a straightshape; or (2) the distal portion has a straight shape and the guidewirehas a stiff pre-shaped spiral shape that includes the pre-shaped spiralradius having the pitch length.
 16. An assembly to be inserted into ablood vessel, the assembly comprising: a sheath, the sheath housing acore capable of at least one of: projecting an optical beam onto aportion of the vessel and receiving a light from the portion of thevessel, the core being movable along the sheath to scan at least aportion of a vessel, the sheath having a plurality of spirals, thesheath being made of a material that is substantially transparent ortranslucent on an outside of the spiral; a support coupled to at least aportion of the sheath, the support capable of changing shape to clear orreduce at least a portion of a signal path between the sheath and thevessel, wherein the guide structure, through lateral movement in a lumenof the elongated sheath, cause the sheath to take the spiral shape; anda control mechanism to facilitate movement of the core through thespirals while imaging, wherein the spiral shape has a pre-shaped spiralradius having a pitch length of the spirals that is selected to be lessthan ten times a known radius of the vessel.
 17. The assembly of claim16, wherein one of the core is to receive a light for an opticaltemperature measurement of the vessel, the core is to project a beam fora photodynamic therapy to the vessel, or the core is to project a beamonto the vessel and receive a reflected light for Optical CoherenceTomography (OCT) scanning.
 18. An elongated assembly, comprising: aproximal portion; and a distal portion, the distal portion to beinserted into a blood vessel, the distal portion controllable throughthe proximal portion, the distal portion comprising: an elongatedsheath, the elongated sheath housing a core capable of emitting anoptical beam for imaging, the core movable along the sheath; and a guidestructure coupled with the elongated sheath, the guide structure beingcontrollable through the proximal portion to increase an overalldiameter of the distal portion from a first overall diameter of a firstconfiguration to a second overall diameter of a second configuration, inthe second configuration the elongated sheath having a substantiallyspiral shape having a plurality of spirals, wherein the core is housedwithin the elongated sheath, the core to project an optical beam and toreceive a reflected light for optical coherence tomography; and whereinthe core is movable along the elongated sheath to scan a portion of thevessel, wherein the spiral shape has a pre-shaped spiral radius having apitch length of the spirals that is selected to be less than ten times aknown radius of the vessel.
 19. The assembly of claim 18, wherein thesheath is made of a material that is substantially transparent ortranslucent on an outside of the spirals, and wherein the guidestructure, through lateral movement in a lumen of the elongated sheath,cause the sheath to take the spiral shape.
 20. The assembly of claim 18,wherein one of (1) the distal portion has a pre-shaped spiral shape thatincludes the pre-shaped spiral radius having the pitch length and theguide structure is a stiff guidewire with a straight shape; or (2) thedistal portion has a straight shape and the guidewire has a stiffpre-shaped spiral shape that includes the pre-shaped spiral radiushaving the pitch length.